Reliability and performance of memory units, including hard disc drives, is improved by arranging multiple memory units in an array, such as a Redundant Array of Independent Discs (or, RAID) system. For example, RAID Level 6 (or, RAID 6) arranges memory units to provide protection for double memory unit failure, and failures when a single memory unit is rebuilding.
Unfortunately, an issue that typically arises for a system such as a RAID 6 system which protects against multiple memory unit failure is that as the array gets larger, the probability of multiple memory unit failure increases, along with the time required to rebuild the failed memory units because of the size of the array. One current way to address this restriction is to split arrays to keep the size manageable, but each split array requires its own additional parity memory units which is expensive. There exists a need for an efficient RAID algorithm that protects against multiple memory unit failure without increasing the time required to rebuild failed memory units or requiring many additional expensive parity memory units.